Rolling mills and methods

ABSTRACT

A multi-roller stand, e.g. three roller, for a rolling line in a rolling mill, e.g. a rod mill, has journalled therein rollers of slightly different diameter. When the rollers become worn the worn larger roller can be refinished and used in the same stand as a replacement for the worn smaller roller. The latter can then be refinished or reground and can replace a still smaller worn roller in the same stand or in another stand, in the latter case as a replacement for a larger roller in said other stand. Alternatively the worn larger roller, after refinishing or reprofiling can be moved to a similar position in another stand higher up the line. In this case a worn larger roller from the first stand can, after refinishing or reprofiling, be used to replace a smaller roller in the last stand.

United States Patent [191 Demny Mar. 27, 1973 ROLLING MILLS AND METHODSPrimary E.mminer--Milton S. Mehr [75] Inventor: Werner Demny,Dusseldrof, Ger- Att0mey Bueu Blenko & zlesenhelm many [ ABSTRACT [73]Assignee: Friedrich Kocks A multi-roller stand, e.g. three roller, for arolling line Filedl y 1971 in a rolling mill, e.g. a rod mill, hasjournalled therein [21] Appl. No; 145,220 rollers of slightly differentdiameter. When the rollers become worn the worn larger roller can berefinished and used in the same stand as a replacement for the [52] U.S.Cl ..72/224 worn smaller roller The latter can then be refinished [5 l]Int. Cl. or reground and can replace a till maller worn roller Field OfSearch 199 in the same tand or in another stand in the latter case as areplacement for a larger roller in said other References Cimd stand.Alternatively the worn larger roller, after refinishing or reprofilingcan be moved to a similar UNITED STATES PATENTS position in anotherstand higher up the line. In this 2,139,872 12/1938 Worthington ..72/203case a worn larger roller from the first stand can, after 3,584,4906/1971 Bindemagel ..72/249 refinishing or reprofiling, be used toreplace a smaller 3,618,354 11/1971 Bindernagel et al ..72/224 ll i h ld 1,810,167 6/1931 George ..72/234 X 11 Claims, 1 Drawing Figure ROLLINGMILLS AND METHODS The invention relates to a rolling mill and method andparticularly to rolling mills having at least one stand with two or morerollers journalled therein to define a sizing gap, wherein the rolls arerefinished and moved to a next position.

In the operation of a rolling mill, the cost of the rollers represents avery important factor. The roller costs can be lowered appreciably byrefinishing or reprofiling the worn rollers and reusing them severaltimes.

In some known multi-stand rolling mills the rollers journallednon-adjustably in one stand are of equal diameter, and afterexperiencing a maximum amount of wear with consequential reduction ofthe ideal diameter, are reprofiled and can be reused by fitting them ina replacement stand having a smaller spacing between the roller axeseither in the same position or in another part of the rolling line. Thepossibility of reuse of the rollers is in this case limited by thenumber of available interchangeable stands provided with differentspacings between the roller axes. It is normally regarded as economic toprovide one set of replacement stands.

In other multi-stand rolling mills with non-adjustable rollers thespacing between the roller axes in the stands of a given row is uniform,so that the rollers which are re-profiled with retention of the idealdiameter, can with their stand be progressively transferred along thewhole row from the output end to the input end. The possibility of reusedepends in this case on the number of stands in one row. After onepassage through the row these rollers cannot be re-used;

The invention is concerned with the problem of procuring still furtherreductions in roller costs in rolling mills of the above-mentioned kind.

According to the invention, the rollers defining one sizing gap compriseat least two rollers of slightly different diameters, such that thelarger of two rollers of different diameters, after experiencing aspecified degree of wear and an appropriate refinishing operation, isfurther usable in the same stand in place of the smaller roller.

In rolling mills of this kind, the rollers, quite apart from the knownmultiple reutilization in different stands after reprofiling, arereusable several times, after the required refinishing, in one and thesame stand, depending on the number of rollers defining one sizing Inthis case the rollers can be progressively transferred from thepositions of rollers of the largest diameter to the positions of rollersof the smallest diameters in the same stands. In order to have optimumconditions for refinishing, the difference in diameter betweendifferent-sized, newly installed or unworn rollers in one stand maycorrespond at least to the sum of the degree of wear permissible for thelarger roller and the grinding loss incurred on refinishing. Thisensures satisfactory conditions for re-finishing to the same rollerprofile.

In the case of rolling mills having several stands arranged one afterthe other in a rolling line, the difference in diameter between twodifferent-sized, newly installed or unworn rollers of the stand at theoutput end of the line may alternatively be so chosen that itcorresponds at least to the sum of the difference in diameter betweenthe larger roller of this stand and the corresponding larger roller ofthe stand positioned at the input end, the permissible degree of wear ofthis roller in the input stand and the grinding loss thereof. In suchrolling mills the sizing gap after reaching the permissible wear limits,may for example be ground to the next sized sizing gap and the wholestand, along with the refinished rollers, can be moved along the rollingline by one rolling station in a direction opposite the direction ofrolling. The rollers are then, only after the stand has passed along thewhole row, themselves interchanged.

In the case of a frequently used type of rolling mill which has severalthree-roller stands in a row, it is advisable to have all three rollersof each stand of different diameters. In stands of this kind therollers, after the required refinishing can be used three times.

In order to facilitate the refinishing of the rollers, the differencesin diameter between the smallest and the middle-sized roller, andbetween the middle-sized and the largest roller are preferably equal.

As a rule, the rollers in a three-roller stand are arranged at relativeto each other, one of the rollers being journalled about an horizontalaxis. The stands, which are located one behind the other, can bealternately inverted by about their horizontal stand axis, so that theroller which is rotatable about the horizontal axis is in one standabove the material being rolled and in the adjoining stands below it. Insuch stands, in which the axes of the three rollers form an equilateraltriangle, the roller displacement of the middle-sized roller ispreferably equal to the quotient of the semi-diameter difference and cos30, while the roller displacement of the largest and the smallestrollers is equal to the product of the roller displacement of themiddle-sized roller and sin 30. This ensures that the height of therolling center remains on the horizontal line through the center of theequilateral triangle formed by the axes of the three rollers, andtherefore lies at the same height as for the case of the symmetricalarrangement of three equal-diameter rollers.

In order to ensure that when the stand is inverted the roll-centeralways remains in the same position, the rolling center can be madecoincident with the standcenter.

The invention is further described, by way of example, with reference tothe accompanying drawing, which is a schematic representation of athree-roller stand in accordance with the invention.

The drawing shows one of a number of three-roller stands of a rod mill.The illustrated stand has three disclike rollers l, 2, 3 whose axes l',2' and 3 form an equi-lateral triangle, with one vertex pointingdownwardly. The peripheries of the rollers l, 2 and 3 are suitablyprofiled to perform the desired working operation on the rod or wirepassing through the mill along the rolling axis. Reference may be madeto copending US. Pat. No. 3,618,354 filed May 6, I970 by Bindernagel andDemny for examples of suitable profiles which may be applied to therollers 1, 2 and 3. However, according to the present invention thediameters of the rollers 1, 2 and 3 differ in length, so that therolling center WM is displaced from the center DM of the triangle.

The middle-sized roller 2 is in the vertical position and in theposition of the stand shown in the drawing it is at the top, while thelargest and smallest rollers 1 and 3 are at 120 to either side and belowthe roller 2. The diameter differences A between the largest and themiddle-sized rollers, and between the middle-sized and the smallestrollers are made equal, so that the rolling center is at the same heightas the center of the triangle.

In order to be able to make unhampered use of the stands in the normalmanner, i.e., according to their position in the rolling line to be ableto turn them upside-down, the rolling center is made the center of thestand, so that on inverting the stand the sizing gap always remains atthe rolling center.

The diameter of the middle-sized roller is called the nominal diameterand has the same magnitude as in the normal symmetrical arrangement, inwhich the three roller diameters are the same. The so-called idealroller diameters for the rollers 1, 2 and 3 are denoted by WD 1, WD 2,WD 3. Let the displacement of roller 1 from the center DM of thetriangle be denoted by a, the displacement of roller 2 by b, and thedisplacement of roller 3 by c. In the example shown in the drawing, inwhich the diameter differences are equal, theroller displacement a ofroller 1 and the roller displacement c of roller 3 are equal.

As can be seen from the drawing, the following geometrical relationshipsapply:

A/2=b.cos 30 (1) a=c=b. sin 30 (2) WDi=WD2+A 3 WG WD DT (5) Thefollowing relationship therefore holds for the i" stand:

WG2,= WD2, DT; (7)

Wc3,= W03, DT,= W02,- A 0T, (8)

The respective values are given a dash if they refer to the worn state,in which case the following relationships hold:

WGl,'= WD2,+A,DT,' (9

WG2 WD2, DT, (10) The magnitude of the maximum permissible wear V isdefined as the difference of the inscribed circles:

V=DT|""DTOI' (l2) A basis for the maximum permissible wear is thedifference of the inscribed circle of two successive sizing gapsmultiplied by a factor smaller than unity. The grinding loss S,- mustalso be taken into account.

The case in which the rollers are interchanged within a given stand hasalso to be considered. The procedure is that, after refinishing, roller1 moves into the place of roller 2 and roller 2 into the place of roller3. Roller 3, which can no longer be reused in this particular stand, isreprofiled and is moved to the next stand in the direction opposite therolling direction,-into which it is fitted as the new roller 1.Similarly, roller 1 of the stand in question is replaced by thereprofiled roller 3 of the stand next in line. The reprofiling of therollers when they are transferred from one stand to the next maycomprise a mere refinishing with the same profile but smaller diameteror may comprise a change in profile as well as a diameter reduction.

In a row consisting of several stands one behind the other, it followsthat only one roller is set free by the stand at the input end and thisroller is no longer usable in the row. At the same time only onecompletely new roller is required by the stand at the output end. In theknown rolling mills at the same point of time three rollers are rejectedat the first stand while three new rollers have to be introduced intothe last stand, so that, with the present invention, the roller costscan be reduced to one third of the previousamount. If two parallel rowswith different ideal diameters are used, the rollers released from thefirst stand of the first row can subsequently be passed through thesecond row, thus again reducing the roller costs by one half.

The diameter differences A of the rollers'at a given sizing gap needonly be very small, so that the rolling performance as compared withthat of rolling mills with equal diameter rollers is not at all orunappreciably impaired. If for example roller 1 is to take the place ofroller 2, the effective diameter of roller 1 in the worn condition mustbe greater than that of roller 2 in the unworn condition by an amountequal to the grinding loss, i.e.,

WGl WG21+ S,

Using equations (7) and (9):

W02, A DT, W02, DT, 3,

Using equation (13) I WD2,+A,DT, V= WD2,DT,+S,

From this we obtain for the diameter difference for the i-th stand:

The diameter difference is determined solely by the permissible wear andthe loss due to the grinding required. For roller 2, which is to be putin the place of roller 3, the same holds good. Therefore the diameterdifferences of the rollers in each of the successive stands in the rowcan be equal.

If in the above equations we substitute actual values,

we obtain values for the diameter differences which are smaller than 1.5mm. The resulting displacements a, b and c of the roller axes turn outto be less than mm.

The peripheral velocities of the three rollers at one sizing gap differfrom each other only by about 0.5 percent. This amount is so small thatit does not require compensation by differences in the speeds ofrotation of the rollers.

According to another method, according to the invention, the rollers arenot interchanged within a single stand, but they are transferred, afterrefinishing or reprofiling, first of all to the same position in thepreceding stand in the direction of rolling. Thus, the roller 1 from thefinal stand is progressively transferred along all of the stands of therow, whereby in each case it takes the place of the former roller 1,until it reaches the stand at the input end of the row. If roller 1 inthe first stand is worn, it is placed, after refinishing or reprofilingin the place of roller 2 of the final stand and is again progressivelytransferred along the whole row of stands in the position of roller 2.Finally, the roller is progressively transferred along the row as roller3.

If in a rolling mill of this kind the stands in a row have the sameideal roller diameters, the stands are interchangeable among themselves.This makes it possible, when the wear limit has been reached, for thesizing gap, as usual in the past, to be ground down to the next largersizing gap. The stand, together with the refinished rollers, is thenmoved to the next position. In the first sizing gap the rollers musthowever be changed round in the stand, whereby roller 1 is put in placeof roller 2 and roller 2 in place of roller 3. Roller 3 is withdrawnfrom the stand and is no longer usable in the row. A new roller has tobe fitted in place of roller 1 of the first sizing gap. This stand, towhich the new roller has been fitted, now has the smallest sizing gapand is transferred to the output end of the row. In this embodiment, thediameter of roller 1 at the sizing gap of the input end, in the worncondition, must exceed the diameter of roller 2 at the sizing gap at theoutput end by an amount equal to the grinding loss, i.e., the sizing gapwith the smallest inscribed circle. In general the following equationholds:

Using equations (9) and (7) and putting k for i in equation (7) we have:

- WD2 +A,-DT,'= WD2,,DT +S Using equation (13):

In this equation we substitute WD2 WD2 giving the following value forthe diameter difference:

It is also however possible to choose different values for the nominaldiameters.

If normal values are substituted in the equations, we have for examplein the case of an eight or l0-stand rolling mill, diameter differencesof less than mm. Under these conditions the peripheral velocities of therollers at identical rotational speeds can differ by more than 3percent. Since differences of this order in the peripheral velocitiescan under certain conditions have an unfavorable effect on theperformance of the rolling mill, it may be desirable to compensate forthe differences in peripheral velocity by altering the gear ratios inthe drives for the rollers.

The same is true for rolling mills, in which, within a row, individualgroups of stands or individual stands have different idea] diameters.The rollers then in the first place pass according to theabove-described method through the stand group on the output end whichhas constant ideal diameters, and are then put in the place of thelargest roller in the last stand of the preceding group, through whichthey can then pass three times. If the group consists only of a singlestand, the rollers move through all of the places in this stand, beforethey are taken to the next stand.

The invention can of course also advantageously be applied to rollingmills having adjustable rollers.

For example, the diameter difference between two different diameterrollers in a given stand which has adjustable rollers, in analogy withthe first abovedescribed method in which the rollers are firstinterchanged in the stand itself, can be equal to the sum of twice theadjustment path of the larger roller plus the wear and grinding losses.In this way the worn large roller, after utilizing the whole adjustmentpath, can in the refinished condition take the place of the smallerroller.

With suitable choice of the diameter differences the rollers may also,by analogy with the second abovedescribed method, be transferred firstof all between each of the stands of a row, or through a group in therow in a specified position, before being placed in the stand at theoutput end in place of the smaller rollers.

The invention is useful in many kinds of rolling mills, e.g. for rollingwire, rods, profiled bars and tubes.

While I have in the foregoing specification set out certain preferredembodiments and practices of my invention, it will be understood thatthis invention may be otherwise embodied within the scope of thefollowing claims.

I claim:

1. In a rolling mill having at least one stand and at least two rollersjournaled therein to define a sizing gap, the improvement comprising atleast two rollers of different diameters in said stand, said differentdiameters being selected so that the larger of said two differentdiameter rollers, after suffering a predetermined loss due to wear, andthe consequential further loss on refinishing, can be used in place ofthe worn smaller roller.

2. In a rolling mill having at least one stand and at least two rollersjournalled therein to define a sizing gap, the improvement comprising atleast two rollers of different diameters in said stand so that thelarger of said two different diameter rollers, after suffering apredetermined loss due to wear, and the consequential further loss onrefinishing, can be used in place of the worn smaller roller and whereinthe diameter difference between said two different diameter unwo'rnrollers is at least equal to the sum of the permissible loss due to wearand the grinding loss on refinishing.

3. A rolling mill comprising a plurality of stands arranged one afterthe other from an input end to an output end, at least two rollersjournalled in each said stand defining a sizing gap, said two rollers ineach stand having different diameters so that the larger of said twodifferent diameter rollers, after suffering a predetermined loss due towear, and the consequential further loss on refinishing, can be used inplace of the worn smaller roller, and in which the diameter differencebetween said two different diameter unworn rollers of the stand at saidoutput end is at least equal to the sum of the diameter differencebetween the larger of said two rollers of the said stand at said outputend and the corresponding larger of the different diameter rollers ofthe stands at said input end, the permissible wear of the said largerroller in the stand at said input end, and the grinding loss onrefinishing thereof.

4. A rolling mill according to claim 3 in which each of said stands hasthree rollers journalled therein, all three rollers of each stand havingdifferent diameters.

5. In a rolling mill having at least one rolling mill stand and at leastthree rollers journalled therein, the improvement comprising at leastthree rollers, all of different diameters, journalled in said stand todefine a sizing gap, said different diameters being selected so that thelarger of said three different diameter rollers, after suffering apredetermined loss due to wear and the consequential further loss onrefinishing, can be used in place of the intermediate diameter rollerofthe three different diameter rollers and the intermediate diameterroller after suffering a predetermined loss due to wear, and theconsequential further loss on refinishing, can be used in place of theworn smallest roller of the three different diameter rollers.

6. A rolling mill stand according to claim 5 in which the difference indiameter between the smallest and the middle-sized of said three rollersis substantially equal to the diameter difference between themiddle-sized and the largest of said three rollers.

7. A rolling mill stand according to claim 6 in which the axes of saidthree rollers define an equilateral triangle.

8. A rolling mill stand according to claim 7 in which one of said rolleraxes is substantially horizontal.

9. A rolling mill stand according to claim 5 including means forinverting said stand about a stand axis coincident with the axis of saidsizing gap.

10. In a rolling mill having at least one stand and at least two rollersjournalled therein to define a sizing gap, the improvement comprising atleast two rollers of different diameters in said stand so that thelarger of said two different diameter rollers, after suffering apredetermined loss due to wear, and the consequential further loss onrefinishing, can be used in place of the worn smaller roller, and inwhich said rollers are journalled non-adjustably in said stand.

11. A method of rolling comprising the steps of:

lpassing a metal strand through a rolling mill having at least one standwith at least two rollers journalled therein of different diametersuntil the rollers are worn to a predetermined extent, refinishing thelarger of said rollers to'replace the smaller roller, and 3. inserting anew roller of the original diameter of said larger roller in place ofthe refinished larger roller and continuing the rolling operation.

1. In a rolling mill having at least one stand and at least two rollersjournaled therein to define a sizing gap, the imProvement comprising atleast two rollers of different diameters in said stand, said differentdiameters being selected so that the larger of said two differentdiameter rollers, after suffering a predetermined loss due to wear, andthe consequential further loss on refinishing, can be used in place ofthe worn smaller roller.
 2. In a rolling mill having at least one standand at least two rollers journalled therein to define a sizing gap, theimprovement comprising at least two rollers of different diameters insaid stand so that the larger of said two different diameter rollers,after suffering a predetermined loss due to wear, and the consequentialfurther loss on refinishing, can be used in place of the worn smallerroller and wherein the diameter difference between said two differentdiameter unworn rollers is at least equal to the sum of the permissibleloss due to wear and the grinding loss on refinishing.
 2. refinishingthe larger of said rollers to replace the smaller roller, and 3.inserting a new roller of the original diameter of said larger roller inplace of the refinished larger roller and continuing the rollingoperation.
 3. A rolling mill comprising a plurality of stands arrangedone after the other from an input end to an output end, at least tworollers journalled in each said stand defining a sizing gap, said tworollers in each stand having different diameters so that the larger ofsaid two different diameter rollers, after suffering a predeterminedloss due to wear, and the consequential further loss on refinishing, canbe used in place of the worn smaller roller, and in which the diameterdifference between said two different diameter unworn rollers of thestand at said output end is at least equal to the sum of the diameterdifference between the larger of said two rollers of the said stand atsaid output end and the corresponding larger of the different diameterrollers of the stands at said input end, the permissible wear of thesaid larger roller in the stand at said input end, and the grinding losson refinishing thereof.
 4. A rolling mill according to claim 3 in whicheach of said stands has three rollers journalled therein, all threerollers of each stand having different diameters.
 5. In a rolling millhaving at least one rolling mill stand and at least three rollersjournalled therein, the improvement comprising at least three rollers,all of different diameters, journalled in said stand to define a sizinggap, said different diameters being selected so that the larger of saidthree different diameter rollers, after suffering a predetermined lossdue to wear and the consequential further loss on refinishing, can beused in place of the intermediate diameter roller of the three differentdiameter rollers and the intermediate diameter roller after suffering apredetermined loss due to wear, and the consequential further loss onrefinishing, can be used in place of the worn smallest roller of thethree different diameter rollers.
 6. A rolling mill stand according toclaim 5 in which the difference in diameter between the smallest and themiddle-sized of said three rollers is substantially equal to thediameter difference between the middle-sized and the largest of saidthree rollers.
 7. A rolling mill stand according to claim 6 in which theaxes of said three rollers define an equilateral triangle.
 8. A rollingmill stand according to claim 7 in which one of said roller axes issubstantially horizontal.
 9. A rolling mill stand according to claim 5including means for inverting said stand about a stand axis coincidentwith the axis of said sizing gap.
 10. In a rolling mill having at leastone stand and at least two rollers journalled therein to define a sizinggap, the improvement comprising at least two rollers of differentdiameters in said stand so that the larger of said two differentdiameter rollers, after suffering a predetermined loss due to wear, andthe consequential further loss on refinishing, can be used in place ofthe worn smaller roller, and in which said rollers are journallednon-adjustably in said stand.
 11. A method of rolling comprising thesteps of: